Flexoelectric effects in a bent α−In2Se3 ferroelectric monolayer

Flexoelectric effects in materials can bring novel physical properties that are absent in their perfect crystal, and have a wide range of applications, such as mechanical sensors and wrinkled triboelectric nanogenerators. In this work, electronic structures and transport properties of bended $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ monolayer are investigated through first-principles calculations and nonequilibrium Green's function (NEGF). We find that two different kinds of type-II band structures can be obtained in $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{P}\ensuremath{\uparrow}$ and $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{P}\ensuremath{\downarrow}$ flexed $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{In}}_{2}{\mathrm{Se}}_{3}$, which show opposite band bending. Carriers in the center of $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{P}\ensuremath{\uparrow}$ and $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{P}\ensuremath{\downarrow}$ flexed $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ are mainly holes and electrons, respectively, which dominate the current behavior of the $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ p-i-n (PIN) field-effect transistor (FET). The $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{P}\ensuremath{\uparrow}$ PIN-FET has enhanced forward current and the rectification ratio due to the larger density of holes. Our study achieves the homogeneous junction through bended $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{In}}_{2}{\mathrm{Se}}_{3}$, which may simplify the device procession and be used as electromechanical sensors.